IMO aikido is very simple - it just takes a long time to realise this, then even longer to be able to achieve this simplicity. I also believe it can't be taught by word of mouth or explained with words and has to be experienced over time. The words are the equivalent of 'pointing at the moon', and shaking the finger harder will not increase the students capacity to understand.

Hi Ian
I agree with this point 'almost' wholeheartedly.
I absolutely agree that aikido is in essence 'simple', and that this is what the student struggles with. Our minds are more comfortable with accumulating knowledge than getting rid of the barriers that prevent effortless aikido.
I do however feel that the words that a teacher uses can help/hinder the students progress in the attempt to achieve aiki.
My own teacher has spent a lifetime refining his teaching technique, and he uses simple and easy to understand speech for all of his students. He seems to have honed his words down to the essence, which I for one really appreciate.
I'm sure that it is possible to completely over complicate the teaching of aikido, especially when there are spiritual and philosophical points to be made along side the mind/body movements.
So while I agree you can't teach solely by word of mouth, the words that come out of ones mouth make all the difference.